Surface charge spectroscopy—A novel surface science technique for measuring surface state distributions on semiconductors

Abstract

A novel technique, surface charge spectroscopy (SCS), has been developed for measuring interface state density at a dielectric-semiconductor interface in conjunction with x-ray photoelectron spectroscopy (XPS). In this technique, a thin dielectric layer with thickness up to 15 nm, is deposited on a semiconductor substrate. The surface Fermi level (E_Fs) of the semiconductor and the surface potential of the dielectric are measured using XPS, the latter of which can be varied by charging the dielectric with electrons from a low energy electron flood gun commonly equipped inside an XPS system. The interface state distribution in the band gap of the sample is then extracted from the relationship between the E_Fs and the dielectric surface potential with a simple space-charage calculation similar to the conventional capacitance-voltage technique. Experimental data on SiO₂/Si and SiN_x/InP samples are shown in the article to illustrate the applicability of SCS.